org.gradoop.flink.io.impl.tlf.functions.TLFFileFormat.java Source code

Introduction

Here is the source code for org.gradoop.flink.io.impl.tlf.functions.TLFFileFormat.java

Source

/**
 * Copyright  2014 - 2018 Leipzig University (Database Research Group)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.gradoop.flink.io.impl.tlf.functions;

import com.google.common.collect.Maps;
import org.apache.flink.api.java.io.TextOutputFormat;
import org.gradoop.common.model.impl.pojo.Edge;
import org.gradoop.flink.io.impl.tlf.TLFConstants;
import org.gradoop.common.model.impl.pojo.Vertex;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.flink.model.impl.layouts.transactional.tuples.GraphTransaction;

import java.util.Map;
import java.util.Set;

/**
 * Converts a GraphTransaction to the following format:
 * <p>
 *   t # 0
 *   v 0 vertexLabel0
 *   v 1 vertexLabel1
 *   e 0 1 edgeLabel
 * </p>
 */
public class TLFFileFormat implements TextOutputFormat.TextFormatter<GraphTransaction> {

    /**
     * Global counter for the graph id used for each single graph transaction.
     */
    private long graphId = 0;

    /**
     * Stores a long representation for each gradoop id.
     */
    private Map<GradoopId, Long> vertexIdMap;

    /**
     * Creates a TLF string representation of a given graph transaction, which
     * has the following format:
     * <p>
     * t # 0
     * v 0 label
     * v 1 label
     * v 2 label
     * e 0 1 edgeLabel
     * e 1 2 edgeLabel
     * e 2 1 edgeLabel
     * </p>
     *
     * @param graphTransaction graph transaction
     * @return TLF string representation
     */
    @Override
    public String format(GraphTransaction graphTransaction) {
        StringBuilder builder = new StringBuilder();

        vertexIdMap = Maps.newHashMapWithExpectedSize(graphTransaction.getVertices().size());

        // GRAPH HEAD
        writeGraphHead(builder, graphId);
        graphId++;

        // VERTICES
        writeVertices(builder, graphTransaction.getVertices());

        // EDGES
        writeEdges(builder, graphTransaction.getEdges());

        return builder.toString().trim();
    }

    /**
     * Converts the graph head into the following format and adds this to the
     * StringBuilder:
     * <p>
     * t # 0
     * </p>
     *
     * @param builder StringBuilder to build the whole string representation
     * @param graphId current graph id
     * @return builder with appended graph head representation
     */
    private StringBuilder writeGraphHead(StringBuilder builder, long graphId) {
        return builder.append(
                String.format("%s %s %s%n", TLFConstants.GRAPH_SYMBOL, TLFConstants.NEW_GRAPH_TAG, graphId));
    }

    /**
     * Converts the vertices into the following format and adds this to the
     * StringBuilder:
     * <p>
     * v 0 vertexLabel
     * v 1 vertexLabel
     * v 2 vertexLabel
     * </p>
     *
     * @param builder StringBuilder to build the whole string representation
     * @param vertices set of vertices
     * @return builder with appended vertex representations
     */
    private StringBuilder writeVertices(StringBuilder builder, Set<Vertex> vertices) {
        long vertexId = 0;
        for (Vertex vertex : vertices) {
            vertexIdMap.put(vertex.getId(), vertexId);
            builder.append(String.format("%s %s %s%n", TLFConstants.VERTEX_SYMBOL, vertexId, vertex.getLabel()));
            vertexId++;
        }
        return builder;
    }

    /**
     * Converts the edges into the following format and adds this to the
     * StringBuilder:
     * <p>
     * e 0 1 edgeLabel
     * e 1 2 edgeLabel
     * e 2 1 edgeLabel
     * </p>
     *
     * @param builder StringBuilder to build the whole string representation
     * @param edges set of edges
     * @return builder with appended edge representations
     */
    private StringBuilder writeEdges(StringBuilder builder, Set<Edge> edges) {
        for (Edge edge : edges) {
            Long sourceId = vertexIdMap.get(edge.getSourceId());
            Long targetId = vertexIdMap.get(edge.getTargetId());

            builder.append(
                    String.format("%s %s %s %s%n", TLFConstants.EDGE_SYMBOL, sourceId, targetId, edge.getLabel()));
        }
        return builder;
    }
}